Method and system for identifying a location for nerve stimulation

ABSTRACT

A system and method for identifying a stimulation location on a nerve is disclosed. The system includes an image-based navigation interface used to facilitate advancing a stimulation element within a patient body toward a target nerve stimulation site. Using the system one determines, separately for each potential target nerve stimulation site, a neuromuscular response of muscles produced upon applying a stimulation signal at the respective separate potential target stimulation sites. The image-based navigation interface is configured to display a graphic identification of which muscles were activated for each respective potential target nerve stimulation site upon applying the stimulation signal.

CROSS-REFERENCE TO RELATED APPLICATIONS

This Utility patent application is a Continuation of U.S. patentapplication Ser. No. 13/634,333, which entered the U.S. National Phaseon Oct. 22, 2012, entitled “METHOD AND SYSTEM FOR IDENTIFYING A LOCATIONFOR NERVE STIMULATION”, and which claims benefit of PCT ApplicationPCT/US11/027956, filed Mar. 10, 2011, entitled “METHOD AND SYSTEM FORIDENTIFYING A LOCATION FOR NERVE STIMULATION” and which claims benefitof Provisional Application 61/313,406, filed Mar. 12, 2010, entitled“METHOD AND SYSTEM FOR IDENTIFYING A LOCATION FOR NERVE STIMULATION” allof which are incorporated herein by reference.

BACKGROUND

Advanced imaging techniques, such as magnetic resonance imaging (MRI),have revolutionized diagnosis and treatment of various patient maladies.In particular, such techniques permit observation of internalstructures, such as soft tissues, that were previously unidentifiable intraditional radiographic techniques (such as X-ray). As such, a widevariety of internal organs, tissues, connective tissue is now viewablealong with the previously viewable bony structures. Using the MRI orother advanced imaging techniques (such as computer tomography, CT),physicians can readily diagnosis or exclude many conditions.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects and features of the present invention will be appreciated as thesame becomes better understood by reference to the following detaileddescription of the embodiments of the invention when considered inconnection with the accompanying drawings, wherein:

FIG. 1 is a schematic illustration of a system and method for navigationvia images and via neuromuscular responses from stimulation, accordingto an embodiment of the present general inventive concept;

FIG. 2 is a flow diagram of a method of navigating placement of astimulation element within a body, according to an embodiment of thepresent general inventive concept;

FIG. 3 is a block diagram of a system for navigation, according to anembodiment of the present general inventive concept;

FIGS. 4-5 are a side plan view schematically illustrating an interfaceof a method and system for graphical differentiation between a targetmuscle and an activated muscle, according to an embodiment of thepresent general inventive concept;

FIG. 6A is a flow diagram of a method of identifying a stimulation sitevia an array of sensor probes, according to an embodiment of the presentgeneral inventive concept;

FIG. 6B is a block diagram of a nerve-muscle response index, accordingto an embodiment of the present general inventive concept;

FIG. 7 is a side view schematically illustrating a method of sensingneuromuscular responses via sensor probes in a head region of a patient,according to an embodiment of the present general inventive concept;

FIG. 8 is a top plan view of a sensor probe, according to an embodimentof the present general inventive concept;

FIG. 9 is a side plan view of a sensor probe, according to an embodimentof the present general inventive concept;

FIG. 10 schematically illustrates a system and user interface fornavigating a pathway via images in relation to neuromuscular responses,according to an embodiment of the present general inventive concept; and

FIG. 11 schematically illustrates a system and user interface fornavigating and tracking a pathway of a stimulation element, according toan embodiment of the present general inventive concept.

FIG. 12 is a schematic illustration of a system and user interface fornavigating a path to implant a stimulation element and simultaneouslyevaluate, via graphic displays, in real-time whether the path orstimulation site is efficacious, according to an embodiment of thepresent general inventive concept.

FIG. 13 is a schematic illustration of a multi-balloon probe and displayof pressure sensed via the probe, according to an embodiment of thepresent general inventive concept.

FIG. 14 is a schematic illustration an illumination system forilluminating anatomical features of a patient, according to anembodiment of the present general inventive concept.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The following detailed description is merely exemplary in nature and isnot intended to limit the present general inventive concept or theapplication and uses of the present general inventive concept.Furthermore, there is no intention to be bound by any expressed orimplied theory presented in the preceding technical field, background,or the following detailed description.

Embodiments of the present general inventive concept are directed toenhancing surgical navigation via combining, in a graphical userinterface, image-based visualization of the soft and hard tissues of arelevant body region simultaneous with graphical representation (withinthe image-based visualization) of muscle activation from a stimulationsignal applied at a target site. In some embodiments, in concert withvisualization of a stimulation element within the image-based navigationinterface, a stimulation path analyzer makes a quantitative evaluationof muscle responses from nerve stimulation to determine a preciselocation of the stimulation element relative to pertinent soft tissues(such as muscles, nerves, and major circulatory vessels) and alsorelative to bony structures, which serve as reference points. With thiscombination, one can determine and visually represent a location of astimulation element in a body region in real time using image-navigationtools simultaneous with functional evaluation of the electrode placement(e.g. does the tongue protrude upon stimulation from the stimulationelement? is the proper muscle group activated?) and simultaneous withquantitative evaluation of the stimulation location, such as nerveconduction and muscle response information (e.g. electromyography and/orcompound muscle action potential).

In some embodiments, the quantitative evaluation information of whichmuscle is activated is expressed within the image-based navigationinterface via highlighting a graphical representation of the activatedmuscle among other muscles and anatomical structures. In one embodiment,the system differentiates between target muscles and non-target musclesin the image-based navigation interface via color, shading, and/or otherpatterns. Accordingly, the system greatly simplifies the role of anoperator by providing real-time representations of the effect of aparticular location of a stimulation element. In one embodiment, thisarrangement is of particular benefit to facilitate percutaneousplacement of an implantable nerve stimulation electrode usable in amethod of treating obstructive sleep apnea or other sleep-breathingdisorders.

These embodiments, and additional embodiments, are described in moredetail in association with FIGS. 1-14 of the present general inventiveconcept.

FIG. 1 is diagram schematically illustrating a system and method fornavigation via images and via neuromuscular responses from electricalstimulation, according to an embodiment of the present general inventiveconcept. In one embodiment, system 20 has particular application tofacilitate a minimally invasive, percutaneous or transvenous placementof an implantable nerve stimulation electrode and thereby avoid atraditional, highly invasive cut-down access procedure.

As illustrated by FIG. 1, system 20 includes interface 30, image-basednavigation module 50, and neuromuscular response evaluator 52. Ingeneral terms, interface 30 includes a graphical user interfaceconfigured to simultaneously display images and neuromuscular responsesin an integrated manner. User controls 34 enable a user to operate andcontrol at least some functions of image-based navigation module 50,parameters of interface 30, and/or neuromuscular response evaluator 52.In some embodiments, on screen controls would be supplemented by one ormore additional control mechanisms, such as foot pedals, voicerecognition commands, a sterilized navi-pad.

In one embodiment, user controls 34 include laser projection onto thepatient and/or onto tissues for identifying anatomical features,landmarks, and distances. In some embodiments, multiple lasers (eachhaving a different color) are used to help differentiate betweenmultiple anatomical features, landmarks, and distances, as furtherdescribed later in association with at least FIGS. 10 and 14.

As illustrated by FIG. 1, interface 30 displays an image 40 of relevantanatomical features of a body portion of patient 22. In addition, asfurther described below, superimposed on the image 40 are muscleidentifiers 42, 44 and a nerve identifier 46, which together indicatewhich nerve is being stimulated, where is it being stimulated, and whichmuscles are activated as a result. In one aspect, nerve identifier 46 isoperable to separately identify multiple nerves to differentiate withininterface 30 each respective nerve, as well as differentiatingidentification of relevant branches of a nerve. In some embodiments,interface 30 additionally indicates a target nerve and a target muscleinnervated by the target nerve, such that interface 30 enablesconfirmation of whether the target muscle or a different muscle has beenactivated via stimulation of a nerve, as will be further described laterin association with FIGS. 4-11.

In one embodiment, the image-based navigation module 50 includes atracking function 60, an imager function 62, a records function 64, andan anatomy map function 66.

In general terms, the imager function 62 obtains and/provides images ofa body portion of patient 22. In some embodiments, the image is obtainedvia an imaging system 80 (not shown to scale for illustrative purposes)including a transmitter 82 and receiver 84, which function together tocapture internal images of patient 22. The imaging system 80 includes,but is not limited to, any one of a magnetic resonance imager (MRI),computer tomography (CT) unit, fluoroscopic imager, endoscopy, etc., orcombinations thereof, as is further illustrated in FIG. 3. In oneexample, endoscopy is used to observe evoked responses.

Records function 64 of image-based navigation module 50 enables accessto one or more stored image records of patient 22, via an electronicmedical records (EMR) system or other resources as further noted inassociation with FIG. 3. Anatomy map function 66 enables access togeneral anatomical maps and images, suitably scaled, to overlay orsuperimpose relative to obtained images of patient 22. In someembodiments, a patient-specific image (such as CT or MRI), is overlaidonto, and synchronized relative to, a generalized anatomy map usingcommercially available image analysis techniques, such as those providedvia Vital Images, Inc. of Minnetonka, Minn. The patient-specific imagesare obtained via known systems such as electronic medical records (EMR)and/or a picture archiving communication system (PACS). In someembodiments, the images are obtained and/or communicated according to aHealth Level 7 standard for electronic medical records.

In this way, a generally comprehensive picture of relevant anatomicalfeatures of a body portion of patient 22 are provided in interface 30(FIG. 1) to facilitate identifying target nerves and muscles whenlocating a target stimulation site for an electrode (or electrode array)and when mapping a percutaneous access pathway to that targetstimulation site.

By utilizing imager function 62, records function 64 and/or anatomy mapfunction 66, the tracking function 60 enables visually tracking (viainterface 30) a location of stimulation element 90 and/or supportinstruments used to guide and place stimulation element 90. In someembodiments, the stimulation element 90 is a stimulation test tool whilein other embodiments, the stimulation element 90 is an implantableelectrode.

In one embodiment, as shown in FIG. 1, the relevant body region ofpatient 22 displayed in interface 30 includes an upper respiratorysystem including the mouth to enable visualizing the tongue, itsunderlying and surrounding muscle groups, related nerve pathways, andsupporting bony structures. In some embodiments, visualization of thesedetailed structures (and their interrelationship) is used to treatsleep-disordered breathing, such as obstructive sleep apnea.

In general terms, the neuromuscular response evaluator 52 of system 20(FIG. 1) is configured to apply a stimulation signal through stimulationelement 90 via a stimulation engine 70 according to stimulationparameters 72. The produced neuromuscular response is sensed with probes92 (for example, probes shown in FIGS. 7-9) and fed to a stimulationpath analyzer 74. Via an electromyography function 76 and a compoundmuscle action potential function (CMAP) 78, the stimulation pathanalyzer 74 differentiates whether the activation of the muscle occurredbecause of stimulation of a nerve innervating that activated muscle orbecause of direct electrical stimulation of the activated muscle. Insome embodiments, at least some of the functions of the responseevaluator 52 are provided via a nerve integrity monitor. In this regard,in one embodiment, the nerve integrity monitor comprises at leastsubstantially the same features and attributes as the nerve integritymonitor described in U.S. Pat. No. 6,334,068, entitled INTRAOPERATIVENEUROELECTROPHYSIOLOGICAL MONITOR, issued on Dec. 25, 2001, and which ishereby incorporated by reference in its entirety. In other embodiments,other commercially available nerve integrity monitors or an equivalentarray of instruments (e.g., a stimulation probe and electromyographysystem) are used to apply the stimulation signal and evaluate theresponse of the muscle innervated by the target nerve.

In some embodiments, a plurality of sensor probes is placed at and nearmuscles to be activated. In one embodiment, the sensor probes comprisefine wire needle electrode typically used in nerve integrity monitoring.With the sensor probes in place and using interface 30, one can observewhich muscles are activated upon stimulation of the different sites andvia path analyzer 74, one can systematically reveal which stimulationsite will result in activation of the desired muscle. This arrangementis described further in association with FIGS. 6A-6B. Accordingly, insome embodiments, system 20 includes a probe docking module 79 toestablish electrical communication between the sensor probes 92,neuromuscular response evaluator 52, and interface 30. Via programming,the probe docking module 79 associates each separate probe 92 with aspecific muscle of the patient 22 so that when the muscle associatedwith a particular probe is activated, the interface 30 can visuallyhighlight that muscle on the displayed image 40. For example,highlighted region 42 of image 40 is associated with probe P2 whilehighlighted region 44 of image 40 is associated with probe P1. In thisway, the interface 30 correlates the location of the sensor probes 92with the anatomical features of the patient 22 in the displayed image40. In some embodiments, this arrangement is facilitated via anerve-muscle index 294, which is further described later in associationwith FIGS. 3 and 6B.

In some embodiments, the stimulation element 90 includes a stimulationtest tool configured to be inserted percutaneously into a body ofpatient 22 to releasably engage a potential stimulation site and enablea stimulation signal to be applied at that site, such as a target nerve.In other embodiments, the stimulation element 90 includes a cuffelectrode (or other electrode configuration) configured to be implantedin a secured relationship relative to a target stimulation site of anerve in order to provide long-term implantable stimulation therapy viaactivation of an innervated muscle. For example, in one embodiment, thetarget nerve is a hypoglossal nerve and the innervated muscle is thegenioglossus muscle. In some embodiments, the target nerve is aparticular branch (or branches) of the hypoglossal nerve. For example,in one example the target nerve includes one or more particular lateralbranches or medial branch of the hypoglossal nerve, such that theinnervated muscle includes the styloglossus muscle, the hyoglossusmuscles, the geniohyoid muscle, and/or the genioglossus muscle.

In one instance, the cuff electrode is delivered to the targetstimulation site of the nerve via minimally invasive, percutaneousaccess (which avoids the more traditional, highly invasive cut-downaccess procedure). As more fully described herein, such percutaneousaccess for cuff electrode is guided via both the image-based navigationmodule 50 and neuromuscular response evaluator 52. In one embodiment,one such percutaneous access method is described and illustrated inco-pending application Ser. No. 61/165,110, filed Mar. 31, 2009, andtitled PERCUTANEOUS ACCESS METHOD AND SURGICAL NAVIGATION TECHNIQUES. Itwill be understood that in some embodiments, other minimally invasivemethods, such as microendoscopic delivery techniques, are used to placethe implantable cuff electrode in cooperation with the guidance of theimage-based navigation module 50 and neuromuscular response evaluator52.

In yet other embodiments, transvenous access delivery methods of astimulation electrode are used to place the stimulation electrode at atarget stimulation site relative to target nerve, and that even thistransvenous delivery is aided or guided via image-based navigationmodule 50 and neuromuscular response evaluator 52 in accordance withprinciples of the present general inventive concept, or in accordancewith other imaging techniques. In one embodiment, one such transvenousaccess method is described and illustrated in co-pending PCT applicationserial number PCT/US2009/059060, filed Sep. 30, 2009, and titledTRANSVENOUS METHOD OF TREATING SLEEP APNEA.

With this arrangement in mind, the produced neuromuscular responses arevisually represented on interface 30 via a highlighted portion of image40, such as via color highlighting or shading. As shown in FIG. 1, thehighlighted portions can take particular shapes and sizes, such asrectangular shapes, that may or may not approximate the general shapeand size of a subject's anatomical features. In some embodiments, thelocation, size, and/or shape of the highlightable portions of interface40 (such as the colored or shaded portions corresponding to a particularanatomical feature) is established at the time that sensor probes areplaced relative to the patient's anatomy.

In the non-limiting example illustrated by FIG. 1, a highlighted portion42 of interface 30 corresponds to a deduced location of an activatedmuscle (i.e., the muscle actually activated, associated with probe P2)while a highlighted portion 44 (associated with probe P1) corresponds toa target muscle that is desired to be activated. Identifier 48highlights the location at which stimulation takes place on nerve 46.Moreover, as the system 10 tracks the real-time location of thestimulation element 90, the location of the stimulation element 90 isdynamically represented via identifier 48 as part of displayed image 40.

With this arrangement, interface 30 simultaneously combines theimage-based navigation information with the neuromuscular responseinformation to provide a real-time indication of which muscles areactivated via stimulation (and to what degree) and a real-timeindication of the location of the stimulation element causing the muscleactivation. Using this information, interface 30 assists a physician inmaneuvering the stimulation element to a target stimulation site for aninnervated muscle to be activated via stimulation.

FIG. 2 is a flow diagram that schematically illustrates a method 100 ofplacing a stimulation element at a target stimulation site, according toan embodiment of the present general inventive concept. In someembodiments, method 100 is performed using substantially the same thesystems, components, modules, functions, etc. as described inassociation with FIGS. 1 and 3-11. In other embodiments, method 100 isperformed using other systems, components, modules, and/or functionsavailable to those skilled in the art.

As illustrated by FIG. 2, method 100 includes advancing a stimulationelement within a body, via an image-based navigation interface, to atarget stimulation site, as at 102. In one embodiment, the stimulationelement is advanced percutaneously while in other embodiments, thestimulation element is guided transvenously or through other accesstechniques. Each potential stimulation site is tested via observingneuromuscular responses produced from a stimulation signal (transmittedby the stimulation element), as at 104. In particular, a neuromuscularmuscle response is determined separately for each potential target nervestimulation site. In a superimposed combination with images of thelocation of the stimulation element among relevant anatomical structures(soft and hard tissues), the produced neuromuscular responses aredisplayed as a graphic identification of which muscle or multiplemuscles were activated from a respective stimulation site, as at 106. Insome embodiments, these muscle responses are recorded for latercomparison to subsequent muscle responses. Further details forperforming aspects of method 100 are described below.

FIG. 3 is a block diagram of a system 200 for providing image-basednavigation of a stimulation element within a body while substantiallysimultaneously graphically identifying a target stimulation site (viathe image-based navigation interface) via neuromuscular responseevaluation, according to an embodiment of the present general inventiveconcept. As illustrated by FIG. 3, system 200 includes image-basednavigation module 210, interface 212, and neuromuscular responseevaluator 214, memory 216, and controller 218. In some embodiments,image-based navigation module 210, interface 212, and neuromuscularresponse evaluator 214 comprise at least substantially the same featuresand attributes as image-based navigation module 50, interface 30, andneuromuscular response evaluator 52, as previously described inassociation with FIG. 1.

In one embodiment, the interface 212 comprises a graphical userinterface 280 configured to display, and enable operation of, thevarious parameters, components, functions, and modules of system 200.Accordingly, via interface 212, system 200 as illustrated in FIG. 3represents the display of the respective parameters, components,functions, monitors, managers, and/or modules as well as representingthe ability to activate or operate those respective parameters,components, functions, monitors, managers, and/or modules.

As illustrated by FIG. 3, image-based navigation module 210 includesimage module 230, records function 64, anatomy map function 66, andfiducials function 256. The image module 230 obtains and provides tointerface 212 one or more of a MRI image 240, a CT image 242, afluoroscopy image 244, and/or an endoscopic image 245 of a pertinentregion of a patient. In some embodiments, aspects of different types ofimages are synthesized or combined to yield a single hybrid image fordisplay at interface 212. In one aspect, anatomical structures (such as,but not limited to, nerves and muscles) are located manually, andhighlighted to the user at interface 212. For example, an operator canreview available images of a patient body region and then select orindicate a particular structure of interest. In one non-limitingexample, an operator selects a mandible within several different imagesor different image types so that the images can be integrated in amanner that still visually displays the anatomical structure ofinterest, i.e., the mandible. In another non-limiting example, anoperator selects a nerve of interest from the soft tissues rendered byan MRI or selects the tongue or other upper airway muscles of interestand associates those with placed sensor/monitors. Records function 64and anatomy function 66 comprise substantially the same features andattributes as previously described in association with FIG. 1.

Fiducials function 256 provides for visually tracking one or morefiducial markers that are visibly distinct from tissues on a displayedimage to provide references points that are independent of the tissuesand anatomical structures of interest. In some embodiments, locationsfor placing fiducial markers include one or more of an anterior point ofthe mandible bone, the hyoid bone, the skull, and/or cervical vertebrae.Of course, other or additional anatomical structures can be used as afiducial reference point by placing a marker there. These fiducialmarkers have shapes and/or sizes selected to provide an objectiveorientation within and relative to the anatomical structures of thedisplayed image (e.g., displayed image 40 in FIG. 1) of interface 212.In one embodiment, during an imaging session to obtain images ofrelevant portions of patient anatomy, a radiopaque marker is placed at adesired implant site. Upon later use of fluoroscopy during placement ofan implantable stimulation electrode, the radiopaque marker is easilyidentifiable and used as a general location marker to facilitateplacement of the electrode.

Interface 212 of system 200 includes graphical user interface 280(described above). In some embodiments, interface 212 includes targetnerve identifier 282, target muscle identifier 284, actual nerveidentifier 286, and actual muscle identifier 288, path marker function290, target spot marker function 292, audio identifier module 300,and/or visual identifier module 320.

The actual nerve identifier 286 provides real-time visual identificationof activated nerve(s) while the actual muscle identifier 288 providesreal-time visual identification of activated muscle(s). Meanwhile, thetarget nerve identifier 282 and the target muscle identifier 284 providetime-independent display of a nerve intended to be stimulated and itsinnervated muscles that are intended to be activated. With thesefunctions 282, 284 an operator designates on displayed image (e.g.displayed image 40 in FIG. 1) the respective nerve and muscle that aretargeted. This designation is made via touching the respective portionsof displayed image 40 (when interface 30, 212 includes a touch screen)or otherwise selecting the desired nerve and muscle via user controls 34(such as a cursor navigation/selection or keypad entry).

In some embodiments, activation of path marker function 290 causesinterface 212 to display a path through which the stimulation element 90is expected to travel percutaneously (or otherwise internally in thebody) as mapped out by an operator on a displayed image (e.g. displayedimage 40 in FIG. 1) based on a probable target nerve stimulation site ora confirmed target nerve stimulation site. In some embodiments, targetspot marker function 292 is provided to allow selective designation on adisplayed image (e.g. displayed image 40 in FIG. 1) of a general orspecific intended target site for placement of an implantable electrode.The accuracy of the target spot is confirmed or denied via thecorroboration of neuromuscular response evaluation, and the target spotmarker can be adjusted accordingly until an accurate target spot islocated. Moreover, via target spot marker function 292, travel along thepath is confirmed or evaluated by applying stimulation and observingwhich muscles are activated.

In some embodiments, the audio identifier module 300 comprises a hitfunction 302, a miss function 304, and/or an intensity function 306. Ingeneral terms, the audio identifier module 300 is configured to provideauditory identification of whether the intended target nerve isstimulated or not. In particular, feedback from which innervated muscleor muscles have been activated (via neuromuscular response evaluator214) is communicated via an auditory signal, auditory words, or othereasily recognizable auditory information. In some embodiments, theauditory alert occurs simultaneous with the period of activation of themuscle being stimulated. This auditory information communicates to theuser whether the target nerve was activated or not. In some embodiments,this information is communicated as an audible alert by a spoken word,such as “hit”, for activation of the target nerve (via hit function 302)and as a spoken word, such as “miss”, for activation of a nerve otherthan the target nerve (via miss function 304).

The intensity function 306 of audio identifier module 300 provides anaudio-based indication of an intensity of the muscle activation producedvia nerve stimulation. In one aspect, this audio report is used toevaluate the intensity of the muscle response based on a given targetnerve stimulation site This audio-intensity information communicates tothe user a relative degree of stimulation of the target nerve, andrelative effectiveness of a particular stimulation site on the nervegiven a nominal set of stimulation parameters. In one example, arelatively low volume audio sound indicates a relatively low-to-moderatemuscle activation to the operator while a relatively higher volume audiosound indicates a relatively high or robust degree of muscle activation.In addition, it will be understood that, depending upon the stimulationparameters, the relative effectiveness of a particular stimulation sitemight vary. Accordingly, in some embodiments, at each particularpotential stimulation site along a nerve, the stimulation parameters arevaried in an organized manner to fully evaluate the effectiveness ofthat potential stimulation site in activating an innervated muscle. Theintensity of muscle activation for each different combination ofstimulation parameters and/or stimulation site is reported to theoperator via audio cues by audio identifier module 300.

To maximize the available information for decision making duringpercutaneous delivery of an implantable electrode or during initialdetermination of a stimulation site, in some embodiments the audioidentifier module 300 is used in concert with the visual identifiermodule 320. However, it is understood that in other embodiments, justone of these respective identifier modules 300, 320 can be used. Instill other embodiments, the audio identifier module 300 and the visualidentifier module 320 are used simultaneously, but independent from eachother.

With further reference to FIG. 3, in some embodiments, the visualidentifier module 320 comprises a color function 322, a shading function324, a numerical intensity function 326, a directional function 328,and/or a traced path function 330. In general terms, the visualidentifier module 320 is configured to provide visual identification ininterface 212 (such as interface 30 of FIG. 1) of whether the intendedtarget nerve is stimulated or not. In particular, feedback from whichinnervated muscle or muscles have been activated (via neuromuscularresponse evaluator 214) is communicated via visual signals, visual wordsor symbols, or other easily recognizable visual information. This visualinformation communicates to the user whether the target nerve wasactivated or not. While this visual information can include graphicaldisplay of a signal normally associated with electromyography, in someembodiments, the displayed visual information omits ordinary waveformsignals in favor of words, symbols, and other more readily identifiableinformation about the status of a particular muscle. In other words,visual identifier module 320 converts or evaluates the quantitative dataof the EMG response and/or CMAP response into a qualitative form thatquickly communicates, in a visually intuitive manner, to the operatorwhich muscle has been activated and/or the intensity of the muscleresponse.

In one example, as noted above in association with FIG. 1, the visualidentifier module 320 provides a graphical representation by which anactivated muscle becomes highlighted on an image in a navigationinterface such that the user can immediately recognize which muscle hasbeen activated.

The color function 322 of visual identifier module 320 provides acolor-based indication of which muscle is activated via nervestimulation and/or a degree of muscle activation produced via nervestimulation. This visual-intensity information communicates to the usera relative degree of stimulation of the target nerve, and relativeeffectiveness of a particular stimulation site on the nerve given anominal set of stimulation parameters. In some embodiments, one coloridentifies a target nerve to be stimulated or a target muscle to beactivated while a second color identifies which nerve is stimulatedand/or which muscle is activated via a stimulation signal. In oneembodiment, when the stimulated nerve matches the target nerve, a thirdcolor overlays the graphical representation of that target nerve toindicate that the target nerve was successfully located and wasstimulated. Similarly, when the activated muscle matches the targetmuscle, the third color overlays the graphical representation of thattarget muscle to indicate that the target muscle was successfullylocated and was stimulated. It will be understood that the same colormay be used for both nerves and muscles, or in other embodiments, thatone set of colors is used to exclusively represent nerves and anotherdifferent set of colors is used to exclusively represent muscles. Ofcourse, it will be understood that other designations of colors can beused to communicate on a displayed image (e.g. displayed image 40 inFIG. 1) which muscles are actually activated via stimulation, whichmuscles are intended to be activated, and/or the degree of activation.

The shading function 324 of visual identifier module 320 provides avisual-based indication of which muscle is activated via nervestimulation and/or a degree of muscle activation produced via nervestimulation. A type of shading or a relative darkness of shadingcommunicates to the user a relative degree of stimulation of the targetnerve, and relative effectiveness of a particular stimulation site onthe nerve (given a nominal set of stimulation parameters). In someembodiments, one type of shading is used to identify muscles and anothertype of shading is used to identify nerves.

In cooperation with the color function 322 and/or the shading function324, the numerical intensity function 326 of visual identifier module300 provides a visual-based numerical indication of an intensity of themuscle activation produced via nerve stimulation. This visual-intensityinformation communicates to the user a relative degree of stimulation ofthe target nerve, and relative effectiveness of a particular stimulationsite on the nerve given a nominal set of stimulation parameters.

It will be understood that, depending upon the stimulation parameters,the relative effectiveness of a particular stimulation site might vary.Accordingly, in some embodiments, at each particular potentialstimulation site along a nerve, the stimulation parameters are varied inan organized manner to fully evaluate the effectiveness of thatpotential stimulation site in activating an innervated muscle.

In one embodiment, the directional function 328 enables visualindication of directional movement of a stimulation element 90. However,in some embodiments, the directional function 328 provides a suggesteddirection in which to move the stimulation element. In this latterarrangement, the path analyzer 374 of neuromuscular response evaluator214 evaluates the positive or negative outcome of the most recentstimulation sites (and the parameters of stimulation at those sites) andbased on any recognized trends or patterns (from prior stimulationtrials), then communicates a suggested direction of movement of thestimulation element. In one embodiment, the suggested direction isdisplayed graphically as a directional arrow on the displayed image(e.g. display image 40 in FIG. 1).

The traced path function 330 enables visual indication of a path ofdifferent previously tested stimulation sites and/or display of a paththrough which a stimulation element 90 is maneuvered through a bodyportion on the way to or from a stimulation site (or other targetlocation).

With further reference to FIG. 3, in some embodiments, interface 212includes a probe module 340 configured to track (based on a location ofrelevant EMG sensor probes and/or piezoelectric accelerometers) a targetmuscle, non-target nerves, and non-target muscles. In one embodiment, atarget muscle parameter 346 of probe module 340 tracks, via a pluralityof sensor probes configured to be removably coupled relative to acorresponding plurality of potentially activatable muscles, eachpotentially activatable muscle that is innervated by one of thepotential target nerve stimulation sites. A non-target nerve parameter344 of probe module 340 tracks, via a plurality of sensor probesconfigured to be removably coupled relative to a corresponding pluralityof potentially activatable muscles, each potentially activatable musclethat is physically adjacent one of the potential target nervestimulation sites and that is not targeted to be activated. Finally, anon-target muscle parameter 342 of probe module 340 configured to track,via a plurality of sensor probes configured to be removably coupledrelative to a corresponding plurality of non-target muscles, eachnon-target muscle that is physically adjacent one of the target muscles.

In general terms, the neuromuscular response evaluator 214 of system 200enables stimulation of nerves and muscles to identify a nervestimulation site. In one embodiment, the neuromuscular responseevaluator 214 includes a stimulation parameters module 350, a responsemodule 352, and a stimulation element module 354.

In general terms, the stimulation parameters module 350 provides forselection of the various parameters of a nerve stimulation signal. Inone embodiment, the stimulation parameters module 350 includes a pulsewidth parameter 360, frequency parameter 362, an amplitude parameter364, a polarity parameter 366, and a duration parameter 368. Each ofthese parameters can be varied, as known by those skilled in the art, toachieve a desired stimulation signal on a nerve. The value of each ofthese parameters may vary from one stimulation site to another. It willalso be understood, that in some embodiments, that a ground connectionto the patient's body and a positive electrode will be used to enable,applying stimulation via a unipolar probe and identifying muscularresponses.

The response module 352 provides for a mechanism to sense, record, andquantify neuromuscular responses of an activated muscle. In oneembodiment, the feedback is sensed, recorded, and quantified viaelectromyography (EMG) via EMG function 380 while in some embodiments,the feedback is sensed, recorded, and quantified via compound muscleaction potentials (CMAP) via CMAP function 382.

The stimulation path analyzer module 374 of response module 352 (ofneuromuscular response evaluator 214) provides for differentiationbetween sources of stimulation of a sensed muscle response. Inparticular, a sensed muscle response can be caused by electricalstimulation of a nerve that innervates the muscle or by directelectrical stimulation of the muscle. Accordingly, the stimulation pathanalyzer module 374 is configured to sort data from the electromyographyfunction 370 according to the stimulation parameters and navigation data(from image-based navigation module 210) to make this differentiationbetween nerve stimulation and direct muscle stimulation. Upon tryingvarious potential stimulation sites, the path analyzer module 374provides a graphical summary of which locations cause nerve stimulationand which cause direct muscle stimulation. With this information, atarget stimulation site is selected.

In particular, in cooperation with EMG function 370 and by observingdata produced via the compound muscle action potential (CMAP) function372, the analyzer module 374 automatically determines if there is a timedelay between the electrical stimulation and the ensuing muscleactivation. In particular, if direct electrical stimulation wasperformed on a target muscle, then no delay would be expected betweenthat stimulation and the ensuing muscle activation. However, ifelectrical stimulation was performed on a target nerve, then a delaywould be expected between that stimulation and the ensuing muscleactivation. In one example, an approximately 100 microsecond delay wouldbe expected for each 1 centimeter distance that the muscle is locatedaway from the nerve. As described later in association with FIG. 6B,this muscle response time is tracked via a nerve-muscle index 294.

The ability to automatically differentiate between electrical nervestimulation and direct muscle stimulation via path analyzer 374 greatlyfacilitates percutaneous determination of a location of a targetstimulation site of a target nerve because, in that situation, the usertypically does not have direct physical sight of the nerves and/ormuscles at which the stimulation tool is directed. However, via theanalyzer module 384, system 200 is able to determine which nerve ormuscle is being stimulated, and which muscle is activated as a result.Upon attempting stimulation at several different locationspercutaneously with the stimulation element, the user determines whichanatomical structure (e.g. target nerve) at which an implantableelectrode should be located and at which location or position along thatnerve the electrode should be secured.

Moreover, once the target stimulation site is determined, the user canfurther utilize system 200 to determine a pathway through which theelectrode can be delivered percutaneously to arrive in the desiredposition at the target stimulation site.

In some embodiments, the analyzer module 374 determines astrength-distance curve for activation of target muscle groups. In oneaspect, the strength-distance curve includes a graphic representation ofthe relationship between an intensity of the electric stimulation siteand a distance between the actual stimulation site and the target nerve.Accordingly, using this strength-distance curve, a distance is estimatedbetween the location of the stimulation element and the activated nerve(or activated muscle). This distance information is used by thephysician to determine how much further, and in which direction, tomaneuver the stimulation element to arrive at the desired location orposition relative to the target stimulation site. In some embodiments,this information is communicated via directional function 328 ofinterface 212. In addition, once a final placement of the stimulationelement (e.g. cuff electrode) is determined, a strength-duration curveproduced via analyzer module 374 (in association with CMAP function 372and EMG function 370) facilitates a physician (or programming unit) insetting efficacious stimulation therapy settings to treat a physiologiccondition, such as sleep-disordered breathing behaviors.

In some embodiments, system 200 includes a nerve-muscle index module 294configured to correlate observed muscle response behavior with anassociated nerve innervating the respective muscles. This index 294 canaid in placing sensor probes and/or in identifying a stimulation sourceupon observed muscle responses. In some embodiments, the interfacestores in memory an array of nerve-muscles indices with a separatenerve-muscle index for each separate patient body portion. In addition,in some embodiments, a nerve-muscle index for a particular patient bodyportion is loaded into a memory of the system prior to performing amethod of percutaneously advancing a stimulation element into andthrough that particular body portion. Further details regarding thenerve-muscle index 294 are described and illustrated later inassociation with FIG. 6B.

In some embodiments, response evaluator 352 also comprises an ultrasounddetection function 375 which is configured to detect muscle motionaccording to Doppler principles. For example, via an ultrasound sensornode placed underneath the chin, ultrasound detection function 375detects motion of the genioglossus muscle in response to stimulation ator near a target stimulation site. In another example, via an ultrasoundsensor node placed at the jaw, ultrasound detection function 375 detectsmotion of the styloglossus muscle in response to stimulation at or neara target stimulation site. Information gained via the ultrasounddetection function 375 is deployed in at least muscle motion parameter476 in nerve-muscle index 294, as later described in association withFIG. 6B.

Stimulation element module 354 provides for applying electricalstimulation via a test tool 380 and/or an implantable electrode 382. Inmost instances, the test tool 380 is employed by the physician to firstidentify the target nerve(s) and target muscle(s) in cooperation withthe other functions, modules of interface 212 and system 200.Thereafter, using the image-based navigation interface providedaccording to general principles of the present general inventiveconcept, the electrode 382 is delivered percutaneously to the targetstimulation site with or without the assistance of test tool 380. Itwill be understood that in such a procedure, the patient is underanesthesia and without using muscle relaxants.

In either case, in some embodiments, the stimulation element module 354includes a handle control portion 384 for guiding test tool 380 orelectrode 382. The handle control portion 384 includes an on/offfunction 386, increase function (+) 388, decrease function (−) 390,pause function 392, and mode function 394. The respective increase anddecrease functions 388,390 provide for a corresponding increase ordecrease in the stimulation parameters (such as amplitude, pulse width,etc.) while the pause function 392 allows temporary suspension of thestimulation signal. The mode function 394 allows selecting various modesof stimulation, such as continuous, intermittent, or discrete (just whenan input button is pressed). In some embodiments, the mode function 394includes an automatic ramping function to determine the parameters360-368 of module 350 of stimulation (such as amplitude, pulse width,frequency, polarity, duration) needed to recruit the targeted nerve andinnervated muscles. Accordingly, this automatic ramping functionprovides information regarding the efficaciousness of the currentstimulation location and the observed muscle responses. For example, amuscle response to a direct electrical stimulation of the muscle isgenerally less than a muscle response to electrical stimulation of thenerve that innervates the particular muscle. In another example, lowerstimulation amplitudes required to produce a muscle response generallyindicate that a stimulation element is close to the target nerve,whereas higher stimulation amplitudes required to produce a muscleresponse generally indicate that a stimulation element is further fromthe target nerve than desired.

Controller 218 comprises one or more processing units and associatedmemories 216 configured to generate control signals directing theoperation of system 200 and its components. For purposes of thisapplication, the term “processing unit” shall mean a presently developedor future developed processing unit that executes sequences ofinstructions contained in a memory, such as memory 216 or other memory.Execution of the sequences of instructions causes the processing unit toperform steps such as generating control signals. The instructions maybe loaded in a random access memory (RAM) for execution by theprocessing unit from a read only memory (ROM), a mass storage device, orsome other persistent storage. In other embodiments, hard wiredcircuitry may be used in place of or in combination with softwareinstructions to implement the functions described. For example,controller 218 may be embodied as part of one or moreapplication-specific integrated circuits (ASICs). Unless otherwisespecifically noted, the controller is not limited to any specificcombination of hardware circuitry and software, nor limited to anyparticular source for the instructions executed by the processing unit.

FIG. 4 is side view schematically illustrating an image-based userinterface that visually identifies muscle activation, according to anembodiment of the present general inventive concept, for use inpercutaneous navigation and/or percutaneous placement of a stimulationelement. As illustrated by FIG. 4, image 400 graphically depicts a bodyportion 402, such as a head-neck region of a patient. The body portion402 includes bony structures 410 that support a group 420 of muscles andtissues. In the example shown, bony structures 410 include a lower jawportion 414 that supports a tongue 412 and its underlying muscles,including (but not limited to) a stylo-glossus muscle 421, agenio-hyoideus muscle 422, a genio-glossus muscle 423, a hyo-glossusmuscle 426, and a stylo-hyoideus muscle 428.

In one embodiment, the genioglossus muscle 423 as shown in FIG. 4 is atarget muscle that is desired to be activated. In particular, activationof this genioglossus muscle 423 contributes to protrusion of tongue 412forward, thereby increasing airway patency near the base of the tongue.In some instances, this protrusion produced via activating thegenioglossus muscle 423 is used to treat sleep-disordered breathingbehaviors, such as obstructive sleep apnea. In one embodiment, thedesignation of this muscle as a target muscle is graphically depictedvia a pattern 424A.

As further shown in FIG. 4, instead of target muscle 423 beingactivated, the hyo-glossus muscle 426 is activated, as graphicallydepicted via a pattern 427.

By displaying this juxtaposition of pattern 424A for target muscle 423and pattern 427 for the actually activated muscle 426, the interface(30,212) provides an immediately recognizable differentiation betweenthe activated muscle and the target muscle, and thereby indicates thatthe stimulation site did not result in activation of the target muscleand indicates which muscle (e.g. muscle 426) was activated. Thisdifferentiation informs the user that a different stimulation siteshould be selected.

In some embodiments, upon such differentiation, system 200 (FIG. 3)suggests graphically (e.g. via highlighting) which nerve to stimulateinstead of the previously stimulated nerve or directly stimulatedmuscle. Moreover, in some embodiments, this suggestion is communicatedvia directional arrows, as provided via directional function 328 ofvisual identifier module 320 (FIG. 3).

FIG. 5 schematically illustrates substantially the same features andattributes as FIG. 4, except for illustrating that the activated muscle(represented by dotted pattern 427) substantially coincides with thetarget muscle (represented by cross-shaped pattern 424A). Alternatively,an entirely different graphical pattern can identify the convergence ofthe activated muscle and the target muscle.

This arrangement provides easier and more effective indication to a userof when a target stimulation site has been located by visuallyidentifying the corresponding innervated muscle upon its activation.Moreover, interface 212 graphically displays via highlighting whichnerve was stimulated and, via a graphical marker or highlighting, theprecise location along that nerve at which the stimulation was applied.Moreover, even after the stimulation element is selectively deactivated,interface 212 allows the user to mark (or automatically marks) thestimulation site, such as via target spot marker function 292.

In some embodiments, the graphical patterns 424A, 427 are replaced withshading via shading function 324 and/or replaced with color via colorfunction 322 of visual identifier module 320 (FIG. 3).

FIG. 6A is a flow diagram schematically illustrating a method 450 ofidentifying a target stimulation site, according to an embodiment of thepresent general inventive concept. In one embodiment, method 450 isperformed using the systems, components, and modules as previouslydescribed in association with FIGS. 1-5. In some embodiments, othersystems and components are used to perform method 450.

As shown in FIG. 6A, method 450 includes placing sensor probes ontovarious portions of a patient body portion in order to removably coupleeach sensor probe relative to a respective one of a plurality of musclesof the patient body portion. These muscles can include a target muscleinnervated by a target nerve, non-target muscle(s) adjacent a targetelectrode site along the target nerve, and/or non-target musclesadjacent the target muscle(s), as shown at 452. Placement of sensorprobes on these non-target muscles allows sensing the activation of thenon-target muscles adjacent either the target nerve site or the targetmuscle, which is in turn, indicative of sub-optimal electrodepositioning relative to a target nerve site. When graphically identifiedin an image-based navigation interface (or via direct observation of afunctional result, such as tongue protrusion) sensing activation of thenon-target muscles provides feedback to re-position the stimulationelement toward the target nerve site.

Accordingly, sensor probes are placed at locations of muscles near thenerve to be stimulated and locations of muscles (or muscle groups)likely to result in muscle activation, whether or not those muscles arethe target muscles. With the sensor probes arranged in this manner, uponimplementing the nerve stimulation a displayed image (e.g. displayedimage 40 in FIG. 1) in interface 30, 212 will highlight which musclesare activated for each trial stimulation, as noted below.

In one embodiment, method 450 proceeds from the sensor probe placementat 452 to use a test tool (not an implantable electrode) for iterativeinsertion to stimulate potential sites while observing neuromuscularresponses, as highlighted on displayed image (e.g. displayed image 40 ofFIG. 1) of interface 30, 212 to identify a probable target site and/or aprobable percutaneous pathway to the target site. Thereafter, at 454,method 450 proceeds to advancing an implantable nerve stimulationelectrode to a probable target site via image-based navigation whilesimultaneously provoking and observing neuromuscular responses. However,in performing method 450, one need not use the test tool (at 454) priorto advancing the implantable electrode within the pertinent body region(at 456).

In one embodiment, method 450 is performed in association withnerve-muscle index 294 (FIGS. 3 and 6B), among other resources of system200. In one aspect, the nerve-muscle index 294 provides a basis to builda graphical user interface (e.g. user interface 30, 40 of FIG. 1) byadding the monitored tissues to the skeletal outline. The nerve-muscleindex 294 also provides an additional portion of interface 30 (asdescribed later in association with FIG. 12) or alternate view (such asFIG. 6B) that supplements the visual representation of the currentlocation of the stimulation electrode and sensor probes (in interface30) by supplying a checklist of which muscle groups are activated orinactivated.

As illustrated by FIG. 6B, in some embodiments, the nerve-muscle index294 comprises an array 460 of primary parameters and an array 470 ofcorroborating parameters. The array 460 of primary parameters includes anerve parameter 462, a muscle response parameter 464, and a probeparameter 466. The nerve parameter 462 maintains a list of nerves of thepatient body portion while the muscle response parameter 464 maintains alist of muscles that respond to and that are innervated by a respectiveone of the listed nerves. In addition, the muscle response parameter 464tracks an amplitude of muscle response for a particular muscle uponnerve stimulation. By comparing different stimulation sites and anamplitude of the muscle response (such as through electromyography), onecan map the location of a target nerve. The probe parameter 466maintains a listing of the various sensor probes that are removablycoupled to the respective muscles with each sensor probe matched to aparticular muscle. Accordingly, via index 294, each listed muscle iscorrelated to one of the respective sensor probes and relative to arespective one of the potential target nerves that innervate therespective listed muscle.

With further reference to FIG. 6B, in one example, via index 294, alateral branch of the hypoglossal nerve is correlated with astyloglossus muscle and sensor probe number 1. Accordingly, when aresponse is observed for sensor probe 1, the system automaticallydetermines that the response is for the styloglossus muscle and anaccompanying graphical identification is made on the user interface tovisually highlight the activation of that muscle. In another example,via index 294, a medial branch of the hypoglossal nerve is correlatedwith a genioglossus muscle and sensor probe number 2. Accordingly, whena response is observed for sensor probe 2, the system automaticallydetermines that the response is for the genioglossus muscle and anaccompanying graphical identification is made on the user interface tovisually highlight the activation of that muscle. As further illustratedin index 294, additional nerves or nerve branches are listed, such asthe main trunk of the hypoglossal nerve, which activates several musclegroups, and which is associated with multiple sensor probes distributedacross the multiple muscle groups. Accordingly, in cooperation withinterface 40 (FIG. 1), nerve-muscle index 294 enables an operator todifferentiate which nerve branch is being stimulated, among multiplepotential target nerve branches, and therefore, responsible foractivation of a particular muscle group or muscle groups.

The array 470 of corroborating parameters is used to confirm theidentity of the muscle that was activated and/or whether the muscleactivation resulted from nerve stimulation or direct electricalstimulation of the muscle. In some embodiments, the array 470 ofcorroborating parameters includes a muscle response time parameter 472,a visible muscle response parameter 474, a twitch response parameter476, and a functional result parameter 478.

In some embodiments, the response module 352 of interface 212 (FIG. 3)is configured to confirm that the target nerve identified via thenerve-muscle response index caused the activation of the respectivelisted muscle. In one embodiment, this confirmation is executed via aresponse time function and tracked as a response time parameter 472 inindex 294. The response time parameter indicates the amount of timebetween a stimulation of a nerve and when the response is observed atthe muscle (innervated by that stimulated nerve). This information isused to determine whether the activation of muscle was caused byelectrical stimulation of the nerve or by direct electrical stimulationof the muscle, as the direct electrical stimulation of the muscle wouldresult in a response time of near zero.

Moreover, the response time of a particular muscle depends on thelocation of stimulation along the nerve and its respective branches.Conceptually speaking, one can divide the nerve into segments with eachsegment innervating a particular set of muscles. By using the measuredreaction time and observing which muscle group is activated, one candetermine the location of stimulation, and therefore which nerve ornerve branch was stimulated. In some embodiments, in accordance withgeneral principles of the present general inventive concept, thisprocess can be performed in whole, or in part, according to the methodsand systems described and illustrated in association with Testerman U.S.Pat. No. 5,591,216.

In some embodiments, a visible muscle response parameter 474 of index294 is configured to indicate a visible muscle response that a usercould observe, such as whether the tongue retracts which corresponds toactivation of tongue protrusor muscles, such as a styloglossus musclelisted in the muscle response parameter 464. If the observed behaviorupon application of a stimulation signal matches the expected responsefor a target nerve, then one gains assurance that the target stimulationsite has been identified. On the other hand, if the observed behaviorupon application of a stimulation signal does not match the expectedresponse for a target nerve, then one learns that the target stimulationsite has not been identified. In the latter case, upon repositioning astimulation element, a subsequent stimulation signal is applied toactivate a muscle and the response is observed to evaluate whether thetarget site has been identified.

In some embodiments, the muscle motion parameter 476 of index 294 isconfigured to track whether motion of the muscle can be detected,whether or not that also results in a highly visible response (suchretraction or protrusion of the tongue). In one embodiment, thedetectable muscle motion parameter 476 tracks muscle responses viaultrasound sensor nodes that detect muscle motion via Dopplerprinciples. For example, in response to a stimulation of a nerve, motionof the genioglossus muscle is detectable via an ultrasound sensor nodeplaced underneath the chin while motion of the styloglossus muscle isdetectable via an ultrasound sensor node placed through the jaw. Incooperation with interface 40 and ultrasound detection function 375 ofresponse evaluator 352 of system 200 (FIG. 3), a correspondinganatomical feature (e.g. nerves and muscles) is highlighted in image 30(FIG. 1), in index 294 (FIG. 6B), or combined interface 700 (FIG. 12)upon ultrasound detection of motion for a particular muscle or nerve.

In another embodiment, the detectable muscle motion parameter 476 trackswhether a twitch response of a muscle is observed, which can furthercorroborate which nerve was stimulated by which muscle responds via thetwitch.

Likewise, the functional result parameter 478 of index 294 is configuredto identify what functional result (e.g. an increased or a decreasedpercentage of airway patency) would be observed upon activation of aparticular muscle, which in turn helps to determine if the target nerveor portion of the target nerve was stimulated. For example, observationand/or measurement of the cross-sectional area of upper airway patencyindicates whether the desired muscle response is achieved in response toa test stimulation at a target nerve site. In another example, afunctional result tracked via parameter 478 includes a relative amountand location of air pressure within the upper airway 810 as indicatedvia a multi-sensor catheter probe 820, as illustrated in FIG. 13. Asshown in FIG. 13, the multi-sensor probe 820 extends within upper airway810 and includes an array of linearly arranged pressure-sensitivesensors 822 programmed to separately indicate a measured pressure ateach sensor 822. Upon an obstruction occurring in the airway 810, theair pressure adjacent one or more of the sensors 822 will besignificantly impacted, and thereby indicate a location of theobstruction along the airway. In one embodiment, each separate sensor822 comprises a mini-lumen exposed to the air within the upper airwayand in communication with a pressure transducer so that the air pressureis measurable at each location of the respective sensors 822 along thelength of probe 820, thereby indicating the air pressure at differentlocations within the airway. In some other embodiments, each sensor 822comprises a balloon-like structure adapted to measure the air pressureat each location of the respective sensors 822.

FIG. 13 also illustrates an image 830 displayable in a user interface,such as interface 30 in FIG. 1 or in functional result display 710 ofinterface 700 in FIG. 12, as will be described further. Image 830displays an image 840 of airway 830, with the airway 830 schematicallyor graphically divided into segments 842 with each segment 842 generallycorresponding to a location of a sensor 822. Based on the sensedpressures, image 840 indicates a location of obstruction from asleep-related breathing disorder (such as obstructive sleep apnea) viahighlighter indicator 845. This information is also used to evaluatewhether stimulation of a target stimulation site on a nerve, results ina muscle response that opens the airway 830 in the vicinity of likelyobstruction, such as marked visually via identifier 845.

In one embodiment, information available from nerve-muscle responseindex 294 (such as the corroborating parameters of array 470) isgraphically displayed at the user interface at the time that a muscle isstimulated to aid the user in identifying corroborating information,such as a twitch or functional result, by reminding the user whatbehavior is to be observed.

In some embodiments, in addition to the image 40 being displayed ininterface 30 (FIG. 1), a nerve-muscle index (including at least some ofthe features of nerve-muscle index 294 of FIG. 6A) is displayed ininterface 30 along with image 40 and/or alternately with image 40. Thedisplayed index lists a plurality of muscle groups for which a responseis expected upon application of the stimulation signal, such as thelistings in index 294. In some embodiments, the displayed indexincludes, but is not limited to, one or more of: (1) a description of anexpected muscular response resulting from application of the stimulationsignal at the target site; (2) highlighting, upon activation via thestimulation signal, at least one of the respective muscle groups listedin the index; and (3) data surrounding the muscular response includingat least one of a response time and a response amplitude. In addition tosupplementing the information displayed via image 40 in user interface30, the nerve-muscle index aids in displaying or identifying to theuser, which muscle group has been activated in the event that thegraphical display of the activated muscle in image 40 is difficult tosee.

In some embodiments, the nerve-muscle index 294 also lists one or moremuscle groups for which stimulation is neither desired nor expected. Tothe extent that these respective muscle groups do not become highlightedin the nerve-muscle index 294, the physician receives assurance thatundesirable neuromuscular stimulation is avoided. However, in the eventthat such undesirable neuromuscular stimulation does occur and thatparticular muscle group was highlighted, the nerve-muscle index 294provides one warning mechanism to alert the physician of undesirablestimulation.

In some embodiments, the nerve-muscle index 294 is storable in memoryand suitable for printing to provide a record of the navigation processand/or implantation procedure of an implantable stimulation electrode.

In one embodiment, an interface 700 that includes a combination of image40 and nerve-muscle index 294 is described and illustrated inassociation with FIG. 12. As shown in FIG. 12, interface 700 includesthe interface 30 (FIG. 1), the interface 400 (FIG. 4), nerve-muscleindex 460 (FIG. 6B), each having substantially the same features andattributes as previously described and illustrated in association withthose respective Figures. In addition, in some embodiments, interface700 further includes functional result display interface 710. As shownin FIG. 12, interface 710 includes an image 720 of an anatomical feature(e.g., a cross-sectional view 722 of the upper airway viewable viaendoscopy) pertinent to observing a functional result of stimulating atarget nerve. Interface 710 also includes a size parameter 730, a shapeparameter 732, a location parameter 731, a motion parameter 734, and asource function 740. The size and shape parameters 730, 732 track achange in the size or shape of an anatomical feature. For example, anupper airway can exhibit a general reduction in its cross-sectional areawhile maintaining a generally circular cross-sectional shape oralternatively could exhibit a significant reduction in itscross-sectional area as the generally circular shape disappears as theairway generally collapses. The location parameter 731 tracks a generalanatomical location and/or a specific location on an anatomical featureat which a functional result can be observed or measured. The motionparameter 734 indicates whether or not motion has occurred (e.g. doestongue protrude?) upon stimulation at a target site.

The source function 740 tracks a source by which an image (or othergraphical display) of a functional result is obtained or produced. Insome embodiments, source function 740 includes an endoscope parameter741, an air pressure parameter 742, an ultrasound parameter 743, anEMG/CMAP parameter 744, and an impedance parameter 745. Each respectiveparameter 741-745 provides information consistent with the previouslydescribed sensing or detecting functions. For example, ultrasoundparameter 743 provides information available via ultrasound detectionfunction 375 (FIG. 3) while air pressure parameter 743 providesinformation available via multi-balloon catheter probe 820 (FIG. 13).

In general terms, interface 710 offers a highly integrated display tofacilitate navigation of a stimulation element and/or related tools bygraphically displaying anatomical features (e.g., bones, tissues, etc.)and the instruments in the field of navigation in real time as theinstruments are moved along a navigation path. Moreover, at the sametime, interface 710 displays, in real-time, a functional visualizationof whether a given path or nerve stimulation test site produces adesired functional result of the intended or target muscle. Thisfunctional visualization is coordinated with images of the navigationfield so that the navigational information and the functional resultinformation is displayed in a single interface to aid the operator withreal-time information that facilitates more accurate navigation andplacement of a stimulation element or test tool. As further illustratedin FIG. 12, nerve-muscle index 460 provides additional text informationin real-time to aid the operator in quickly corroborate thevisual/graphic information displayed at interfaces 40, 400, or 710 ininterface 700. For example, index 460 in FIG. 12 includes a highlightingfunction 750 in which a nerve or innervated muscle of interest (such asa nerve being stimulated) is highlighted in index 460 (represented byshading) and which corresponds to a highlighted nerve and/or innervatedmuscle in interface 40, 400, or 710. It will be understood that, in someembodiments, interface 700 is selectable controllable to display asubset of the interfaces 40, 400, 710 and index 460, at the discretionof the operator.

FIG. 7 is a side view schematically illustrating an arrangement 500 ofplaced sensor probes (510, 512) for detecting impedance changesindicative of a functional response of a target muscle, according to anembodiment of the present general inventive concept. In particular, FIG.7 illustrates a head region 502 of patient and in particular, an oraland neck region including tongue 522 and airway patency-related muscle520. In one aspect, probe 510 is placed on tongue 522 while probe 512 isplaced under the jaw adjacent airway patency-related muscles 520. Withthis arrangement, impedance is measurable with the two probes 510, 512such that changes in impedance can be used to quantify movement of thetongue. In particular, increased impedances to the electrodes near thefront of the tongue and the back of the airway would be indicative of asubstantial forward movement of the tongue.

In general terms, correct placement of a probe can be confirmed byapplying stimulation to one probe and then sensing the response fromother probes or observation by a physician. While some probes may not beplaced in ideal locations, it will be understood that whateverinformation is obtained from these probes is used to help determine orcorroborate an intended navigation path and/or identification of atarget stimulation site.

FIGS. 8-9 further illustrate a sensor probe 540 (that can act as probe510 and/or 512) according to an embodiment of the present generalinventive concept. FIG. 8 is a top view of probe 540, which includes agenerally elongate flexible body 542 made of (or coated with) abiocompatible material. In some embodiments, probe 540 includes aplurality of anchors 544 that extend from opposite side portions 543 ofbody 542 and are spaced apart from each other longitudinally along alength of body 542. Each anchor 544 includes a pressure sensitiveadhesive on its underside to allow secure direct adhesion relative to asurface body portion. However, in other embodiments, it will beunderstood that any number of different types of fasteners can be usedwith, or in place of, anchors 544. In some embodiments, additionalfastening is achieved via coating the underside 547 of body 542 withadhesive.

FIGS. 8-9 further illustrate that probe 540 includes an array of finegauge needles 546 arranged in a spaced apart relationship along thelength of body 542, and extend away from an underside 547 of body 542.In one embodiment, the needles 546 extend generally perpendicular to theunderside 547 of body 542 although in other embodiments, needles 546 canextend at different angles relative to underside 547.

While FIG. 7 provides one schematic illustration of probe placement, itwill be understood that can have more than two sensors and that sensorscan be placed in other locations. For example, as described previously,in some embodiments, some sensor probes are placed at the target musclegroups (i.e. the intended muscle to be activated) to confirm that thedesired muscle group is activated and to obtain data re stimulation,muscle response, etc. In addition, in some embodiments, sensor probesare placed at muscle groups near the target nerve to facilitate optimalelectrode placement. In particular, an observed activation of a musclenear the target nerve site would indicate a likely sub-optimal electrodeplacement at the target nerve, and thereby trigger the physician toadjust the placement of the electrode.

FIG. 10 is a schematic illustration of an image-based visualizationsystem 600 used in a method of identifying a target stimulationlocation, according to an embodiment of the present general inventiveconcept. As shown in FIG. 10, system 600 includes an image module 602and graphical user interface 604. In one embodiment, system 600corresponds to a StealthStation™ type imaging system available fromMedtronic of Fridley, Minn. As shown in FIG. 10, image module 602provides internal images of anatomical structures of a body region, withimage module 602 including a front view 610, a side view 612, a top view614, and a plan exterior view 616. The front view 610 and top view 614illustrate a body region including a tongue portion 620 and a nerve 622.Marker 630 provides an independent reference point, such as a fiducialmarker. The side view further illustrates the tongue portion 620 andnerve 622, although showing the various muscle groups (see also FIGS.4-5) supporting tongue portion 620. Using the various views of the imagemodule 602 to collectively provide a three-dimensional view, an operatorcan guide a stimulation element 635 relative to the displayed nerve 622and tongue portion 620. Moreover, the different views of the imagemodule 602 can be displayed in combination with a graphical display(such as image 40 in FIG. 1 or the images of FIGS. 4-5) of activatedmuscles and stimulated nerves (as described in association with at leastFIGS. 1-9), thereby providing real-time indication of the preciselocation of a stimulation element and the effectiveness of thestimulation element at that location for activating a target muscle.

In one embodiment, system 600 includes an array of reflectors placeableon various anatomical landmarks of a patient, on tools (and differentportions of the tools), and the general environment in which the patientis situated. For example, as illustrated in FIG. 14, placement of amarker 880 on a patient's chin provides one such anatomical landmarkrelevant for visualizing procedures in the area of the head and neck.Using an infrared camera, the various locations of the reflectors areidentified and compiled into a three-dimensional map suitable to guidenavigation during an invasive procedure. In some embodiments, system 600further includes a laser projection function 900, as illustrated in FIG.14. Laser projection function 900 projects different colors 902, 904,906 directly onto a patient 910 (based on the infrared anatomicalreference points, other interpolated anatomical positions, and internalimaging information, as described in association with FIG. 10) to guidenavigation of instruments (e.g. a test tool, a stimulation element, apercutaneous access system, a transvenous access system) on an intendednavigational path 912, 914, actual navigational path, and/or intendedtarget 916 of the navigational path, as generally illustrated in FIG.14. In one embodiment, the differently color illumination provided viathe laser projection function 900 is displayed in combination with agraphical display (such as image 40 in FIG. 1 or the images of FIGS.4-5) of activated muscles and stimulated nerves (as described inassociation with at least FIGS. 1-9), thereby providing real-timeindication of the precise location of a stimulation element and theeffectiveness of the stimulation element at that location for activatinga target muscle.

In some embodiment, the color laser projection functionality greatlyfacilitates a transvenous access method of delivery of the stimulationelement and/or test tool, as this method does not include accessing thetarget nerve via surface cutting of tissue.

FIG. 11 is a schematic illustration of an image-based visualizationsystem 600 used in a method of identifying a target stimulation locationand/or navigation pathway, according to an embodiment of the presentgeneral inventive concept. As shown in FIG. 11, system 650 includesinterface 652. In one embodiment, system 650 corresponds to a LocaLisa™type non-fluoroscopic imaging system available from Medtronic ofFridley, Minn. Interface 652 provides a three-dimensional representationof a body region along three orthogonal axes 653 (x), 654 (y), 655 (z).Using surface mounted electrodes arranged about an outer surface of thebody portion, movement of a stimulation element 635 (test tool orimplantable electrode) is tracked along a path 660 of internal locations662 using voltage and impedance information from the surface-mountedelectrodes and the conductive stimulation element 635. A referencemarker 665 provides an independent reference point. With thisarrangement, an image is generated of a navigated path and the locationof the stimulation element 635. In some embodiments, this generatedimage is superimposed with patient anatomy maps and more comprehensiveimages (e.g. MRI), as previously described in association with FIGS.1-9, for display in interface 30, 212 (FIGS. 1,3) to assist in placingthe stimulation element.

It will be understood that different combinations of the components ofthe image and navigation interfaces can be made, such as but not limitedto, including or excluding a nerve-muscle index 294 (FIGS. 6B and 12)with an image interface 40, including or excluding a functional resultmodule, or even including or excluding a sensor probe interface.

Embodiments of the present general inventive concept provide for dynamicreal-time identification of muscle activation from electricalstimulation in context with image-based navigation tools, therebyenhancing placement of stimulation element within a body portion of apatient.

While at least one exemplary embodiment has been presented in theforegoing detailed description, it should be appreciated that variationsexist. It should also be appreciated that the exemplary embodiment orexemplary embodiments are only examples, and are not intended to limitthe scope, applicability, or configuration of the present generalinventive concept in any way. Rather, the foregoing detailed descriptionwill provide those skilled in the art with a convenient road map forimplementing the exemplary embodiment or exemplary embodiments. Itshould be understood that various changes can be made in the functionand arrangement of elements without departing from the scope of thepresent general inventive concept as set forth in the appended claimsand the legal equivalents thereof.

1. A method identifying a stimulation location on a nerve, the methodcomprising: advancing a stimulation element within a patient body, viaan image-based navigation interface, toward a target nerve stimulationsite; determining, separately for each potential target nervestimulation site, a neuromuscular response of muscles produced uponapplying a stimulation signal at the respective separate potentialtarget stimulation sites; and displaying, within the image-basednavigation interface, a graphic identification of which muscles wereactivated for each respective potential target nerve stimulation siteupon applying the stimulation signal.
 2. The method of claim 1, whereinadvancing a stimulation element comprises at least one of: advancing thestimulation element percutaneously; or advancing the stimulation elementtransvenously.
 3. The method of claim 2, comprising: locating the targetstimulation site at at least one of a main branch or a medial branch ofthe hypoglossal nerve.
 4. The method of claim 3, comprising: furtherlocating the target stimulation site to activate at least one of agenioglossus muscle group, a geniohyoid muscle group, a styloglossusmuscle group, or a hyoglossus muscle group.
 5. The method of claim 1,wherein displaying the graphic identification of the activated musclescomprises: displaying a plurality of muscles, including the activatedmuscles, for a region of the patient body; and highlighting theactivated muscles from among non-activated muscles of the plurality ofdisplayed muscles.
 6. The method of claim 5, wherein displaying thegraphic identification of the activated muscles comprises: visuallyindicating a degree of response by the activated muscles via at leastone of: displaying a different color for each different degree ofresponse; displaying a different degree of shading for each differentdegree of response; or displaying a different numerical identifier foreach different degree of response.
 7. The method of claim 6, comprising:highlighting the respective target nerve stimulation sites thatcorrespond to the activated muscles using substantially the same visualindication that was displayed for the activated muscles.
 8. The methodof claim 1, comprising: displaying a graphic identification of therespective target nerve stimulation sites corresponding to the activatedmuscles.
 9. The method of claim 1, wherein displaying the graphicidentification of the activated muscles comprises: visually indicating adegree of response by the activated muscle via at least one of:displaying a different color for each different degree of response; ordisplaying a different degree of shading for each different degree ofresponse.
 10. The method of claim 1, wherein displaying the graphicidentification of the activated muscles comprises: indicating a degreeof response of the activated muscle via producing an auditory alertsimultaneously with the period of activation of the respective activatedmuscle.
 11. The method of claim 10, comprising: providing the auditoryalert to include a word-based auditory alert, wherein a first word-basedauditory alert indicates that a target muscle has been activated and asecond word-based auditory alert indicates that a non-target muscle hasbeen activated.
 12. The method of claim 1, wherein determining theneuromuscular response of muscles comprises: removably coupling, priorto applying the stimulation signal, a plurality of sensor probesrelative to a corresponding plurality of potentially activatablemuscles, with each potentially activatable muscle being innervated byone of the potential target nerve stimulation sites.
 13. The method ofclaim 12, comprising: providing the sensor probes as ultrasound nodesensors.
 14. The method of claim 12, comprising; providing the sensorprobes as at least one of electromyography electrodes or a compoundmuscle action potential electrodes.
 15. The method of claim 12,comprising: providing the sensor probes as a combination of electrodesarranged to measure impedance.
 16. The method of claim 12, whereindetermining the neuromuscular response comprises: removably coupling,prior to applying the stimulation signal, a plurality of sensor probesrelative to a corresponding plurality of non-target muscles, with eachnon-target muscle being physically adjacent one of the target muscles.17. The method of claim 1, wherein advancing the stimulation elementcomprises: providing the stimulation element as a test tool; and whereindetermining the neuromuscular responses comprises iteratively:inserting, for each separate potential target nerve stimulation site,the test tool percutaneously to be electrically coupled relative to therespective potential target nerve stimulation site; and upon eachdetermined neuromuscular response, repositioning the test tool to beelectrically coupled to another one of the respective potential targetnerve stimulation sites.
 18. The method of claim 17, wherein uponidentification of the target nerve stimulation site from among thepotential target nerve stimulation sites, visually marking on theimage-based navigation interface a location corresponding to the targetnerve stimulation site; while maintaining the test tool in the patientbody at the target location and using the test tool as a guidemechanism, advancing an implantable stimulation electrode percutaneouslyto position the implantable stimulation electrode at the target nervestimulation site; and removing the test tool while maintaining theimplantable stimulation electrode at the target nerve stimulation site.19. The method of claim 18, wherein removing the test tool from thepatient body comprises: marking, with the test tool in position at thetarget nerve stimulation site, a surface of the patient body an entrypoint at which the test tool enters the surface.
 20. The method of claim1, wherein advancing the stimulation element within the patient bodycomprises advancing the stimulation element transvenously, and whereindetermining the neuromuscular responses comprises iteratively:maneuvering, for each separate potential target nerve stimulation site,the stimulation element transvenously within the vasculature to beelectrically coupled relative to the respective potential target nervestimulation site; and upon each determined neuromuscular response,repositioning the stimulation element to be electrically coupled toanother one of the respective potential target nerve stimulation sites.